** 0.0 / 5 ? ChemistryElectrode potentialsA2/A-levelOCR Created by: GemmaCreated on: 11-04-14 14:58 Definition of a ligand A negatively charged ion/neutral molecule with a lone pair of electrons 1 of 34 Colour of Zn (s) and Ag (s) grey 2 of 34 Colour of Cu2+ (aq) blue solution 3 of 34 Colour of Zn (aq) & Ag (aq) colourless 4 of 34 Colour of Cu (s) orange 5 of 34 Why is a platinum electrode used in some half cells? When different oxidation states of the same element in an aqueous solution are present - when there's no metal 6 of 34 Define standard electrode potential The potential difference between a metal ion/metal half cell and the standard hydrogen half cell 7 of 34 Which way do the electrons flow in en electrochemical cell? From the anode to the cathode (- to +) 8 of 34 How do you Calculate the standard electrode potential of the electrochemical cell (E cell) s.e.p of the most positive - s.e.p. of the least positive 9 of 34 Standard conditions for the half cell 1 atm, 1 mol dm-3 , 298K 10 of 34 Why might a reaction not happen at standard conditions, even though it may theoretically be feasible? rate of reaction might be very slow 11 of 34 What can be done to make sure the reaction occurs /is feasible + problem? Could use a catalyst - this will speed up the rate of reaction, but the electrode potential value will change as it is not under standard conditions 12 of 34 In the process of rusting , what happens to the oxygen + where does it occur? Oxygen is reduced to OH- , at the side of the water drop 13 of 34 In the process of rusting, what happens to the iron + where does it occur? Iron becomes oxidised to Fe2+ , this happens at the centre of the drop 14 of 34 Where does the rust form? at the sides of the water drop 15 of 34 Where is the iron eaten away in rusting? the middle - it is being oxidised 16 of 34 What increases the process of rusting? The presence of salt (NaCl) - increases the conductivity of the water , so it occurs more quickly. Also acidic conditions speed up the reaction 17 of 34 What is the formula of rust? Fe2O3*xH2O 18 of 34 What is the definition of a transition metal? a d block element which can form one/more stable ion with a partially filled d sub shell 19 of 34 Colour of Fe2+ green 20 of 34 Colour of Fe3+ yellow 21 of 34 Colour of Cu2+ blue 22 of 34 Reaction of Cu2+ and OH- + colour Cu2+ + (OH)2 ==> Cu(OH)2 blue solution 23 of 34 Reaction of Fe2+ and OH- + colour Fe2+ + (OH)2 ==> Fe(OH)2 green gelatinous precipitate 24 of 34 Reaction of Fe3+ and OH- + colour Fe3+ + (OH)3 ==> Fe(OH)3 orange gelatinous precipitate 25 of 34 Colour of [Cu(H2O)6]2- blue 26 of 34 Colour of [CuCl4]2- yellow 27 of 34 Colour of [Cu(NH3)4 (H2O)2] 2- deep blue/violet 28 of 34 Why are copper + chromium arranged in the way they are? To arrange themself so a lower energy level is required 29 of 34 Definition of monodentate + example when ligands can only bond to a metal ion through a single atom/ion e.g. H2O/NH3 30 of 34 Definition of bidentate + example ligands can form 2 bonds with a metal ion (using pairs of electrons from 2 oxygen /nitrogen atoms) e.g. ethanedioate ion 31 of 34 Definition of polydentate + example ligands can bond through more than one atom e.g. EDTA 32 of 34 Why TM can act as homogeneous catalyst? TM have various oxidation states which can form intermediate compounds 33 of 34 Why TM can act as heterogeneous catalysts? Their ability to use electrons from 3D + 4S sub shell to form weak bonds with the reactants 34 of 34
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